In an effort to protect Earth's environment and to conserve natural resources, the reduction of greenhouse gas emissions has been identified as a priority by governments around the world. One way to reduce greenhouse gas emissions is to reduce energy consumption. The consumption of energy can be reduced by using energy efficient devices, including illumination devices.
Optical illumination devices and systems using planar or slab light guides are energy efficient illumination devices. Such illumination devices typically include various layers of optically transmissive layers or media. Conventionally such illumination devices may be divided into a layer that receives and guides light from one or more light sources for insertion into a layer that redirects the light for emission from the illumination device. Depending on the configuration and construction of a particular illumination device, these layers may be areas of a unitarily manufactured structure or may be separate physical structures that have been separately manufactured and subsequently brought together to form a single structure that operates as a unit. Where the layers are manufactured separately and are subsequently assembled to form a unit, the optically active elements of the unit must be carefully aligned, therefore a high degree of precision is required in the assembly of each illumination device.
An energy efficient illumination device that is simpler to manufacture is therefore desirable.